The edges of mattresses, box springs, seat cushions and other upholstered items are typically subjected to added stresses and strains as compared to the body of the mattress or like device. The edges bear the added force associated with sitting on and standing up from the edge. These forces are also more concentrated at the edge during rising and sitting, since the remainder of the spring assembly typically is not involved, and therefore does little to distribute the forces.
The edge areas are therefore subjected to greater compression forces than the body of the item. The greater compression forces and added stress and strains to which the edges of a mattress, in particular, are subjected to often cause these areas to wear much more quickly than the main body of such items. This type of wear results in tipping or side sway effects about the border of the mattress. Wear of this type reduces the full comfort of the item, and results in unevenness.
It is thus desirable to reinforce and provide greater stability to the edges of a mattress or similar spring cushion assembly. Products with reinforced borders have been developed to reduce early wear about the edge of a mattress or like device, and otherwise stabilize the border.
For instance, U.S. Pat. No. 3,848,283 discloses a mattress in which a rectangular frame elastic foam is fit into void spaces left in the sides of the spring coil assembly. The foam frame is held in place by its own contraction and an outermost covering which envelopes the whole mattress body.
Another device, shown in U.S. Pat. No. 3,822,426, has a combined mattress topper pad and border stabilizer which is formed as a single unitary member having a mattress topper pad portion and a border stabilizer portion. One or more slits are provided in the stabilizer portion to fit the generally rectangular cross-sectioned frame onto the springs.
U.S. Pat. No. 3,618,146 discloses a border stabilizer formed from a plurality of foam strips which are positioned along the peripheral row of spring coils. Each strip is slit to fit over one or more convolutions of the outermost coils.
None of the previously disclosed mattresses and border stabilizers, however, provide for a border stabilizer that does not extend beyond the spring border of the spring coil unit. These prior art devices also use a plurality of frame strips that must be sized to the particular unit, or a single unitary foam frame that likewise must be generally sized to the unit for a proper fit. The necessity to stock the various size foam strips is undesirable, as is the alternative of cutting a foam strip to size. Moreover, handling and forming multiple strips increases the time and labor in assembly.